This invention relates to a hydraulic torque impulse generator, comprising a drive member connected to a rotation motor, a cylindrical fluid chamber in said drive member partly defined by a circumferential wall of a nonconstant radius, an output spindle rotatably supported in a coaxial relationship with said drive member and comprising a rear portion which extends into said fluid chamber, said rear spindle portion having one or more radial slots each supporting a radially movable seal element for sealing cooperation with seal ridges on said fluid chamber wall, thereby dividing said fluid chamber into one or more high pressure compartments and one or more low pressure compartments during short intervals of the relative rotation between said drive member and said output spindle.
In U.S. Pat. Nos. 3,214,941, 3,263,449, and 4,553,948 there are shown and described hydraulic impulse generators with a various number of seal elements which are radially movable in slots in the rear spindle portion so as to maintain a continuous contact with the fluid chamber wall during relative rotation between the drive member and the output spindle. In order to ensure a proper sealing contact between the movable seal elements and the fluid chamber wall there are employed springs to exert radially directed bias forces upon the seal elements. This means that there is always a contact pressure between the seal elements and the fluid chamber wall, also when no sealing cooperation between the seal elements and the fluid chamber wall is to be established. Accordingly, one problem concerned with the above described previous impulse generators relates to mechanical wear of the seal elements in their contact with the fluid chamber wall.
The main object of the present invention is to substantially reduce the mechanical wear of the seal elements. This is obtained by the invention as it is characterized in the claims.
An embodiment of the invention is described in detail with reference to the accompanying drawing figures.